For anyone interested in a Dash Cam for their Lexus, it might be worth your while waiting for the Genuine Lexus Dashcam:
It does appear to be only 1 Channel, but if the price is right you could consider installing 1 for the front and another for the rear.
Seems to have a good spec and does everything the Blackvue does, but would not require the Power Magic Ultra B124 Powerpack for Parking Mode.
Seen adverts for it in Canada but nothing in the UK yet.
My local dealer could not find it on his parts list, but he is investigating.